This invention relates to a solid state color imaging system which produces color video signals by sequentially reading out signal charges that are stored in a number of photoelectric devices responsive to light from an object, and more particularly to an improvement of the solid state color imaging system which can reduce Moire to reproduce pictures of high quality.
Conventionally, an image pickup or camera tube has been used for conversion of light from an object into video signals but in recent years, a solid state image sensor has also been used in this field of art. Various types of solid state image sensors are known. Usually, a number of photoelectric elements such as photodiodes are two-dimensionally arranged in a light sensitive area and signal charges stored in the photoelectric elements are sequentially read out. Charge transfer or coupled devices may be used as the photoelectric elements. In general, signal charges stored in the photoelectric elements in a given horizontal scanning line (or in a given row) are sequentially read out through a signal output line coupled with vertical scanning lines. Alternatively, a charge transfer or coupled device may be connected with the vertical scanning lines for reading out the signal charges to transfer them to its output port. The construction and operation of the above arrangements are well known in the art and hence a further explanation will be omitted.
Different from the image pickup tube, the solid state image sensor does not use deflection coils or plates for electron beam deflection and consequent analog scan but uses clock pulses for digital scan. Accordingly, linearity of scanning is excellent and addresses on the scanned photoelectric plane of the image sensor can readily be related to the electrical signal output.
In constructing a color imaging system with such a solid state image sensor, an optical image is decomposed into three color images by means of a color separation optical system (including prisms or dichroic mirrors), and three image sensors each having a number of photoelectric elements are provided to the respective color images. In this case, the color separation optical system employed is complicated, large-sized and expensive, resulting in impairment of the advantage due to the utilization of the solid state iamge sensor. Further, very stringent standards are disadvantageously required of the color separation optical system in respect of dimensional precision and aberration because linearity and width of scanning are fixed in the digital scan.
Under the circumstances, a stripe color filter arrangement adapted to spacially sample light from an object has been proposed in order that the color separation system may be simplified and the system can be constructed with a single image sensor.
More particularly, it has been proposed to combine a strip color filter 1 comprised of filter elements 1R, 1G and 1B for red, green and blue colors as shown in FIG. 1 with three groups of photoelectric elements (not shown). With such a stripe color filter, however, a profile interferes with the stripe color filter to develop Moire when imaging an object of, for example, scenery which is crowded with electric poles or chimneys, and picture quality is terribly degraded.